GOODWILL AND INTANGIBLE ASSETS - Analysis of goodwill and intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill
Goodwill, gross		$ 42,237	$ 42,237	$ 42,237
Accumulated translation adjustment		4,911	4,911	4,911
Goodwill, net of accumulated translation adjustment	$ 102,003	47,148	47,148	47,148
Impairment charges			0
Acquired during the year	54,855		0
Intangible assets with an indefinite life
Gross amount		26,036	26,036	26,036
Accumulated amortization		0	0	0
Intangible assets with an indefinite life, net	120,784	26,036	26,036
Impairment charges, indefinite lived			0
Acquired during the year	94,748		0
Intangible assets with a finite life
Gross amount		23,030	23,030	29,166
Accumulated amortization	(66,534)	(11,165)	(9,356)	(13,390)
Accumulated translation adjustment		0	0	0
Intangible assets with a finite life, net	344,041	11,865	13,674	15,776
Acquired during the year	387,545		13,330
Amortization	(55,369)	(1,809)	(2,493)
Impairment charges			(12,939)
Total
Gross amount		91,303	91,303	97,439
Accumulated amortization	(66,534)	(11,165)	(9,356)	(13,390)
Accumulated translation adjustment		4,911	4,911	4,911
Goodwill and intangible assets net balance	566,828	85,049	86,858	$ 88,960
Acquired during the year	537,148		13,330
Amortization	(55,369)	$ (1,809)	(2,493)
Impairment charges			$ (12,939)
Intangibles, wind-down of operations	6,136
Accumulated amortization wind-down of operations	$ 7,945